Papers

ICMCTF2001 Session B3-2: Structure/Properties Characterization of Hard Films

Tuesday, May 1, 2001 1:30 PM in Room Golden West

Tuesday Afternoon

Start	Invited?	Item
1:30 PM		B3-2-1 Direct Synthesis of Nanocomposite Thin Films by Ion-Beam Processing P. Bellon, R. Enrique, F. Wu (University of Illinois) While energetic ion beams have been widely used to change the near-surface composition of thin films, the common practice is to rely on thermal annealing to control the distribution of chemical species in the processed layer. Our recent modeling and experimental work, however, establishes that ion-beam processing at a controlled temperature can also be used to tailor new microstructures. In the case of a thin film made of immiscible elements, e.g., Cu and Ag, we show that ion-beam processing at intermediate temperatures (100 to 150 C) stabilizes nanocomposite structures with tunable lengthscales. The relationship between processing conditions and microstructures is studied by XRD, TEM and STEM, while the impact on hardness is followed by nanoindentation.
2:10 PM		B3-2-3 Island Nucleation Kinetics During TiN(001) Growth by Reactive Magnetron Sputtering M.A. Wall, D.G. Cahill, I. Petrov, J.E. Greene (University of Illinois) Polycrystalline TiN thin films are vital in the microelectronics, optical, and hard coatings industries. In addition, TiN(001) is a model system for studying epitaxial crystal growth in the limit of large nucleation lengths and small asymmetry in the adatom attachment rates at step edges. We grow epitaxial TiN(001) thin films using ultra-high vacuum (UHV) reactive magnetron sputtering on single-crystal MgO(001) at temperatures of 650 to 850°C. Temperature-dependant resistivity measurements indicate high crystal quality, with resistivity values equal to the lowest published (ρ=12.5 µΩ-cm at T=300 K to ρ=0.75 µΩ-cm at T=20 K). We characterize the surface morphology using in-situ UHV (~10^-10 Torr) scanning tunneling microscopy (STM). The surface of TiN(001) consists of growth mounds with a surface width of ~1 nm and separated by ~100 nm. We find the critical island size necessary to nucleate a second layer cluster from the STM data and fit the nucleation data using rate equation models for two-dimensional island nucleation on a singular surface and on a growing terrace. From these results, we find the activation energy for surface diffusion to be E_D=0.85 eV and estimate the binding energy of an atom at a kink site to be E_B=1.8 eV. In addition, we show that the transition from a minimum stable cluster size of two molecules to a larger cluster occurs at T=750°C.
2:30 PM		B3-2-4 W-WC Hard Coatings Multilayers for Adhesion Improvement of Diamond Like Carbon (DLC) Thin Films Deposited on Steels: Microstructure and Properties C. Rincon (Universidad Autonoma de Occidente, Colombia); G. Zambrano, P. Prieto (Universidad del Valle, Colombia); J. Esteve, E. Martinez (Universitat de Barcelona, Spain); H. Galindo (Universidad de los Andes, Venezuela) W-WC hard coating multilayers are investigated to be used as intermediate layers for adhesion improvement between the high speed steel substrate and Diamond Like Carbon (DLC) hard coating layer. The W-WC-DLC (Tungsten-Tungsten Carbide-Diamond Like Carbon) hard coatings multilayers were obtained in situ by reactive magnetron sputtering Physical Vapor Deposition (P. V. D.) method starting from a single tungsten (99.99%) and carbon (99.99%) binary compound target. The multilayers deposition starting from a binary compound target is obtained by gradual variation of methane (CH₄)concentration in the Argon-Methane (Ar-CH₄) sputtering gas. Cross-sectional Transmission Electron Microscopy (XTEM) was employed to characterize the interface between different layers and steel substrate. The design of coatings with hard and lubricious Diamond Like Carbon surfaces requires a study of transition between adhesive metal (W), load supporting carbide (WC), and wear-resistant DLC materials. Phase transitions between W-WC-DLC multilayers were analyzed with IR, XPS, XRD and Raman spectroscopy. These phases transitions were reflected in mechanical properties investigated with nanoindentation. The resulting composition was used to design a wear-resistant coating with W-WC-DLC transitions and a gradual increase in hardness from a steel substrate to super-hard (50-60 GPa) self-lubricating DLC layer on the surface. This multilayers deposition allows to avail the optimal adhesion of coatings on the steel substrate, the WC and DLC high hardness and the low friction coefficient of the upper DLC layer
2:50 PM		B3-2-5 IPVD-Created Aluminum Oxide Film at Low Temperature N. Li (Uiniversity of Illinois at Urbana Champaign); D.N. Ruzic, M.J. Neumann (Univeristy of Illinois at Urbana-Champaign) In the conventional reactive deposition of aluminum oxide, the substrate is heated to above 500Â°C to get a desirable phase structure. However Ionized PVD technology is able to make films with comparable properties at a much lower substrate temperature. The introduction of an inductively coupled plasma ionizes the sputtered metal atoms and thus forms a new equilibrium in the association of aluminum and oxygen. The substrate is RF -biased, so the metal ions can be accelerated to the films. The Ionized PVD is performed in a magnetron sputtering system with an additional 7-turn helical resonator coil in the chamber. The substrate is temperature controlled. Located in the same plane of substrate, a gridded energy analyzer (GEA) and a quartz crystal microbalance (QCM) give the deposition rate of deposited films and the ionization fraction of aluminum flux as a function of O2 partial pressure. At 25mTorr total pressure, the ionization fraction is 90%. X-ray diffraction results demonstrate that different phase structures are developed with the variation of ionization of fraction and total pressure. The index of refraction also varies. Chemically bonding and composition of the deposited films were studied by XPS and Auger electron spectroscopy. The dependence of the aluminum:oxygen ratio of the film on the ionization fraction is studied.
3:10 PM		B3-2-6 Synthesis and Mechanical Properties of B-O-C Thin Films D. Music (Linköping University, Sweden); J.M. Schneider (Linköping Unversity, Sweden); V. Kugler (Linköping University, Sweden); S. Nakao, P. Jin (National Industrial Research Institute of Nagoya, Japan); M. Östblom, L. Hultman, U. Helmersson (Linköping University, Sweden) B-O-C thin films have been deposited on Si(100) and graphite substrates by reactive RF magnetron sputtering of a sintered BC_0.11 target. X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy and X-ray diffraction were applied to study the influence of the O₂ partial pressure on the film composition and microstructure. BO_xC_0.11 thin films with x=[0.02-0.21] were formed by varying the O₂ partial pressure from 7.2x10^-7 to 3.3x10^-2 Pa. The film microstructure was X-ray amorphous. Fourier transform infrared spectroscopy showed that the films with the high O content (x≥0.15) contained boric acid (H₃BO₃). Mechanical properties were evaluated by nanoindenation. As x was varied from 0.02 to 0.21, the elastic modulus decreased, by a factor of 2.5, from 272 to 109 GPa which can serve as a tool for tailoring of the mechanical properties. H₃BO₃ surface formation resulted in the decrease of the elastic modulus.
3:30 PM		B3-2-7 Reflectivity Spectra of TiN_x and (Ti,Al)N Coatings M. Zlatanovic, A Kunosic, S Zlatanovic (University of Belgrade, Yugoslavia) The TiN_x and (Ti,Al)N coatings were deposited onto HSS substrates in a magnetron ion plating system at various deposition conditions. The coatings structure and properties were analyzed by XRD, SEM and STM techniques and by measuring the microhardness, critical load for cohesive and adhesive failure and coating thickness by ball grinding test. Reflectivity measurements in the UV-VIS-NIR spectral range were performed using a Perkin-Elmer spectrophotometer with an integrating sphere in 8/d measurement geometry, including specular reflection. From the reflectivity spectra of the TiN_x and (Ti,Al)N coatings in the wavelength range from 300nm-2000nm the screened and unscreened plasma energy, interband transition energies and broadening factors, as well as static optical resistivity were calculated. The optical measurement provided the calculation of the static optical resistivity of the film deposited onto electricaly conductive substrate such as HSS without application of a direct contact electrical method. The minimum resistivity as low as 19.9µΩ was estimated. For additional optical characterization of deposited TiN_x films the ellipsometry was carried out using a Rudolph-Research nulling ellipsometer at the fixed wavelength corresponding to the He-Ne laser emission (λ = 632.8 nm). The coating optical properties were modeled by the screened Drude model and semiclassical model which includes both the intraband and interband electron transitions. It has been demonstrated that the optical reflectivity of the (Ti,Al)N coating may successfully be modeled by the semiclassical relations. This nondestructive technique was proved to be a powerful method for testing optical and some electrical properties of the TiN_x coating.
3:50 PM		B3-2-8 Oxidation Kinetics of Sputtered Cr-N Coatings P.H. Mayrhofer, H. Willmann, Christian Mitterer (University of Leoben, Austria) CrN coatings are nowadays successfully applied for applications where they are subjected to high temperatures. Although the oxidation threshold of hard coatings has been investigated by several authors, there is only limited information on the oxidation kinetics. Within this paper, the oxidation behavior and kinetics of sputtered Cr-N coatings were studied. All coatings investigated were prepared by means of reactive unbalanced DC magnetron sputtering using a Cr target and argon/nitrogen discharges. The N/Cr ratio was systematically varied to achieve coatings with phase compositions of single phase Cr₂N and CrN. For the single phase CrN coatings, the grain size was adjusted to values between 15 and 60 nm using different ion bombardment conditions to evaluate the grain size influence. The oxidation behavior of these coatings deposited onto hot-working tool steel was investigated using thermogravimetric analysis in an argon/oxygen atmosphere. Dynamical measurements were carried out to determine the oxidation threshold and to provide basic information on suitable temperatures for isothermal measurements. The results obtained by the latter were used to calculate the activation energy for oxidation by means of Arrhenius plots. The oxidation products were characterized using scanning electron microscopy, energy-dispersive X-ray analysis and X-ray diffraction. Based on the results obtained in this study it can be concluded that the activation energy for oxidation provides a suitable basis for comparison of the oxidation behavior of different hard coatings.
4:10 PM		B3-2-9 Fabrication, Thermal Stability, and Microhardness of Sputtered Ni-P-W Coating Y.I. Chen (Industrial Technology Research Institute, Taiwan); F.B. Wu (National Tsing Hua University, Taiwan); P.J. Peng (Industrial Technology Research Institute, Taiwan); J.G. Duh (National Tsing Hua University, Taiwan) The ternary Ni-P-W alloy coating was fabricated by the rf magnetron sputtering technique with dual targets of the electroless nickel alloy and the tungsten metal. The composition of both the deposited alloy and sputtered targets were evaluated by electron probe microanalysis. Homogeneity of Ni-P targets fabricated by electroless nickel on the copper plates was revealed from cross section line profile. Transition in microstructure in terms of the tungsten contents in the as-deposited alloy deposit was discussed through X-Ray diffraction technique. Results in microhardness test showed that the surface hardness could be engineered by the control of both composition and microstructure in the Ni-P-W coating. A relatively high microhardness around 1900HK was observed for the ternary coating with high tungsten contents. It was noted that the thermal stability could be enhanced by the addition of tungsten in the deposit as compared to the binary Ni-P sputtered coating.
4:30 PM		B3-2-10 Effect of Substrate Bias on the Structure and Properties of Ion-Plated ZrN on Si and Stainless Steel Substrates J.-H. Huang, C.-Y. Hsu, G.-P. Yu (National Tsing Hua University, Taiwan, R.O.C.) This research studied the effect of bias on the microstructure and properties of zirconium nitride (ZrN) deposited on Si (100) and AISI 304 stainless steel. The ZrN films were deposited using hollow cathode discharge ion plating (HCD-IP) method. The optimum coating conditions were first determined using Taguchi experimental method. Based on the optimum condition, the single-variable experiment on the effect of bias was conducted. The cross-sectional microstructure reveals that the columnar structure of the ZrN film became denser with increasing bias. The results of X-ray diffraction (XRD) show that all the coating samples exhibited (111) preferred orientation both on Si and 304SS substrates. The microhardness values of ZrN films deposited on Si were ranging from 20 to 28 GPa, and on 304 stainless steel were 32.5 to 40.8 GPa. The ZrN films deposited by HCD-IP method were very smooth with a roughness number ranging from 1.1 to 3.9 nm. The N/Zr ratios were close to the stoichiometric composition. The resistivity of ZrN films gradually decreases with increasing bias until -120V and then abruptly increases. The corrosion resistance of ZrN-coated stainless steel was evaluated by standard salt spray test and potentiodynamic scanning in two kinds of solution environments: 5% NaCl and 1N H2SO4 + 0.05M KSCN, respectively. The results show a consistent trend between salt spray test and potentiodynamic scanning. The corrosion resistance increases with bias at bias ranging from 0V to -90V, then abrupt decreases at -120V, and then increases again at -150V. The properties changes of resistivity and corrosion resistance can be explained by the change of film structure due to bias-induced ion bombardment.
4:50 PM		B3-2-11 Hardness and Corrosion Behavior in CrN/Electroless Ni/Mild Steel Complex Coating J.G. Duh, J.S. Chen, F.B. Wu (National Tsing Hua University, Taiwan) The electroless Ni-P coating is introduced as an interlayer to improve the properties of the CrN/mild steel assembly. The acid hypophosphite-reduced bath is applied to deposit electroless Ni-P on mild steel (MS) substrate, and CrN film is further prepared by reactive rf magnetron sputtering on the electroless Ni-P deposited substrate. The electroless nickel layer crystallizes with the precipitation Ni₃P phase due to the elevated substrate temperature during rf sputtering, and thus a coating assembly of CrN/Ni-Ni₃P/MS is formed. Surface hardness of the coating assembly modified by electroless Ni-P interlayer exhibits a value higher than 2000HK under a load of 15gf. The usually substrate effect is nearly eliminated. Through series of corrosion test, it is demonstrated that CrN/Ni-Ni₃P/MS shows a smaller corrosion current along with a more positive corrosion potential. An uniform and well-controlled electroless Ni-P interlayer suffices to provide a better corrosion resistance in the CrN coating on the mild steel.